The present invention relates to the manufacture of typewriters or other office machine keyboards and is particularly directed to a method for producing an inscription on key buttons. The key buttons consist of plastic material which changes colors under the effect of energy radiation.
Using energy radiation, specifically laser radiation, for inscribing various materials has been known for some time. In addition to burning methods where the energy beam causes a melting of the surface, for instance of metallic materials, according to the contours drawn by the beam or where the energy beam changes a coating applied on the part to be inscribed, it is also known, for instance from the German patent document No. 29 36 926, to make the parts to be inscribed from plastic which changes color under the effect of the energy radiation, in its effective area. Cited as an example in said patent document is the inscription of plastic appliance keys which are produced as identical plastic parts, by injection molding using a uniform tool, and which receive their inscription thereafter by energy radiation.
As compared to a key manufacture where the keys are injection-molded in two colors, provided with characters and symbols, the previous laser jet method offers the advantage of reduced inventory and tool costs. But a factor which increases costs is that each individual uninscribed key must be withdrawn from inventory, fed to the inscribing appratus and, after inscription, undergo an intermediate storage for installation in various devices, ordered by characters and symbols.
The problem underlying the invention is to provide a method which further economizes the inscription of key buttons for office machine keyboards.